1. Field of the Invention
The present invention relates to a gaming machine configured to allow one or more players to place one or more gaming media such as gaming chips or gaming cards to which one or more pieces of identification information are assigned respectively, on any of placement areas such as betting areas of a gaming table, and then play a game.
2. Description of the Related Art
Before playing a game such as roulette or card-playing in a game hall such as a casino, a player exchanges money for one or more gaming media such as gaming chips or gaming cards. The player plays the game using one or more gaming media and then cashes one or more gaming media obtained in the game.
For example, in roulette, gaming chips given to each player have colors that differ from ones of other gaming chips given to other players so that a croupier can identify each player at betting time. A numeral or mark related to a value (e.g., 1 cent, 5 cents, 10 cents or 100 cents) of gaming chip is assigned (incused) to the gaming chip so that the croupier can easily identify kinds of gaming chips. The croupier provides one or more gaming chips to each winning player according to values of gaming chips bet on a current game and multiplying power in the current game every time one game is finished. Each player can cash one or more gaming chips obtained in the roulette anytime.
Recently, a gaming medium in which an IC tag is embedded is used in a game. The IC tag stores a unique identification code of the gaming medium and a code representing a value of the gaming medium therein. A system smoothly carries out a game while identifying a unique identification code and the like stored in an IC tag of each gaming medium during the game.
Generally, on a gaming table, a placement area (e.g., betting area) on which one or more gaming media are to be placed is adjacent to other placement areas. If the gaming table is small and/or the number of placement areas is large, each placement area becomes smaller. In this condition, if a lot of players play a game simultaneously, a gaming medium that is placed on a desired placement area and bet by each player is likely to cover on another placement area adjacent to the desired placement area.
In order to surely detect a gaming medium placed on a desired placement area and bet by each player without interfering in a progression of game, a solution using an IC tag embedded in a gaming medium has been conventionally proposed.
For example, patent documents 1 (Japanese Published Unexamined Application No. 2004-105321) and 2 (Japanese Published Unexamined Application No. 2004-102953) disclose a gaming machine configured to arrange X-array antennas for emitting radio waves along an X-direction (e.g., longitudinal direction) of gaming table and Y-array antennas for emitting radio waves along a Y-direction (e.g., lateral direction) of gaming table under the gaming table, so as to read information stored in an IC tag embedded in a gaming medium. When an X-array antenna and a Y-array antenna emit radio waves, a magnetic field is generated in an upward direction vertical to the gaming table at each cross point where a radio wave from the X-array antenna crosses one from the Y-array antenna. The gaming machine reads information stored in an IC tag embedded in a gaming medium placed on a cross point using the magnetic field to detect a placement condition of gaming medium. It is noted that each cross point corresponds to each placement area on which a gaming medium is to be placed.
In the gaming machine, when the detection of placement conditions is carried out, it sequentially scans all cross points while generating a magnetic field in the upward direction at each cross point. At this time, magnetic field lines concentrically diffuse at each cross point according to the corkscrew rule. If the magnitude of magnetic field generated is large, the gaming machine is likely to detect a gaming medium placed on another cross point adjacent to a cross point concerned where the magnetic field is generated in the upward direction because the magnetic field lines return in a downward direction by the diffusion to pass through the another cross point. In this case, the gaming machine incorrectly determines that the gaming medium placed on the another cross point is placed on the cross point concerned.
In order to avoid the above-described incorrect detection, it is necessary to reduce the magnitude of magnetic field by an output control of magnetic field. In the output control, if the magnitude of magnetic field generated is too small, the gaming machine can not detect placement conditions of gaming media which are accumulated on a cross point where the magnetic field is generated. Namely, the gaming machine can not surely read plural pieces of information stored in IC tags embedded in the gaming media which are accumulated on the cross point.